Volatile Material Dispenser and Dispensing Screen Thereof

ABSTRACT

A dispenser for dispensing volatile material by evaporation comprises a reservoir for containing volatile material to be dispensed. The dispenser further comprises a dispensing screen for dispensing volatile material by evaporation, the dispensing screen comprising a sheet of material having continuous first and second edges and forming a continuous loop of material extending between the first and second edges. Communicating means can carry volatile material from the reservoir to an in use upper edge of the dispensing screen. The material of the dispensing means is acutely angled to an in use vertical axis of the dispenser.

The present invention relates to a volatile material dispenser,particularly, but not limited to a dispenser for perfumes, insecticides,insect repellents, anti-viral/bacterial, decongestant inhalant,pheromone and attractant materials.

BACKGROUND OF THE INVENTION

Different types of fragrance dispensers are known. Some consist of apiece of material which is impregnated with volatile scent chemicals.However, although such products initially provide high levels of scentdelivery, this reduces as the concentration of scent chemicals in thematerial reduces. Similar disadvantages exist with gel based airfresheners, in which the fragrance material is provided in a gel andevaporates into the air.

In order to overcome such problems, dispensers in which the volatilematerial is stored in a reservoir and delivered to a dispensing materialare known. In particular, so called “plug in” dispensers are available,in which the volatile material is dispensed with the aid of a heatedwick to encourage evaporation.

Also, a wick can be used to dispense the fragrance from a reservoir.However, as fragrances generally comprise different “notes”, whichevaporate at different rates (“high” notes evaporating more quickly than“bottom” notes), such wicks generally become saturated and clogged withthe least volatile “bottom notes” of the fragrance and the carriermaterial, so that their effectiveness is therefore reduced over time. Afragrance may contain several fragrance components, solvents andresidues. The various components provide the character or profile of thefragrance and they have different volatilities ranging from top note(high) to bottom/end notes (low). Historically perfumers have usedbottom notes to sustain conventional fragrance products over timebecause the volatile top notes tend not to last.

Dispensing insecticides, as opposed to fragrances, requires differentconsiderations due to e.g. their different compositions, differentvolatilities and the loading they produce on a system. As such, systemsdesigned for linearly dispensing fragrances may not also linearlydispense insecticides. Linear dispensing of insecticides is, of course,highly desirable to ensure substantially constant dosage of materialsand effectiveness over the life of the product.

The present invention seeks to overcome or ameliorate at least one ofthe problems associated with the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided adispenser for dispensing volatile material by evaporation. Inembodiments, the dispenser comprises a reservoir, for containingvolatile material to be dispensed. In embodiments, the dispensercomprises a dispensing screen for dispensing volatile material byevaporation, the dispensing screen comprising a sheet of material havingcontinuous first and second edges and forming a continuous loop ofmaterial extending between the first and second edges. Further, inembodiments of the invention the dispenser comprises communicatingmeans, for carrying volatile material from the reservoir to an in useupper edge of the dispensing screen. The material of the dispensingmeans may be acutely angled to a longitudinal axis of the dispenser,which may be an in use vertical axis of the dispenser. In an embodiment,the material of the dispensing means may be positioned at an angle αsubstantially between 15 and 45° to said longitudinal axis of thedispenser. In alternative embodiments, the angle may be up to about 60°or 70°, or down to about 5° or 10°. In embodiments, angle α may besubstantially 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70°.The angle α is defined as the angle between the longitudinal axis and anaxis extending along the direction of the minimum distance between apoint on the first edge and a point on the second edge.

The longitudinal axis may be a rotational axis of symmetry. The acuteangle means that the material of the dispensing means has a radialcomponent and a longitudinal component relative to the axis. The radialseparation of the material from the axis may increase all around theloop of material relative to the axis in cross sections moving along theaxis.

The dispensing screen may be mounted around the reservoir. This providesa compact package as well as placing the top edge of the dispensingscreen close to the top of the reservoir.

The screen may be substantially circular in, in use, horizontal crosssection. The diameter of the screen may increase from the top to thebottom of the screen. Alternatively, it may decrease. Further acombination of increase and decrease in diameter may be provided in thehorizontal cross section of the screen from top to bottom. The screenmay be conical, frustoconical or trumpet shaped, or be comprised of morethan one conical, frustoconical trumpet shape joined together. Thescreen may not be circular in horizontal cross section, but extendlaterally by a greater amount in one closed notional ring than atanother closed notional ring which is substantially parallel thereto.

The dispensing screen may be mounted concentric to the in use verticalaxis of the reservoir, which also provides a compact package for thedispenser.

The dispensing screen may be formed from a sheet of material. Divertingmeans may be provided on the sheet of the screen, which creates aminimum path length along the surface of the sheet, which is longer thanthe shortest distance between the first and second edges. The sheet maybe woven.

The communicating means conveniently comprises a wicking element,extending from inside the reservoir to the first edge of the dispensingscreen. More than one wicking elements may be arranged between thereservoir and the screen, the wicking elements being in communicationwith one another to deliver volatile material from the reservoir to thescreen.

The height of the dispensing screen may be the same or less than theheight of the reservoir, providing a compact package and aiding withprovision of a hydrostatic head.

A second aspect of the invention provides a dispensing screen fordispensing, by evaporation, volatile materials applied theretocomprising a sheet of material. In embodiments of the invention,diverting means is provided, formed in or on the sheet. In embodimentsof the invention, the diverting means form a minimum path length of thesheet for volatile material flowing along it between at least a portionof a first edge and an opposing second edge of the sheet, which minimumpath length is longer than the shortest distance between the first andsecond edges along the surface of the sheet. In embodiments of theinvention, the first and second edges of the sheet are each joined sothat each is continuous, and the sheet is formed into a continuous loopof material between them. In embodiments of the invention, a firstclosed notional ring on the surface of the material has a first lengtharound its circumference and a second closed notional ring on thesurface of the material, substantially parallel thereto and separatedtherefrom, has a second length around its circumference, the secondlength being longer than the first length.

In embodiments of the invention, the area of the cross section throughthe first ring is smaller than the area of the cross section through thesecond ring. In embodiments, the minimum distance from a notional axisthrough both rings of the first ring is smaller than the minimumdistance from the same notional axis of the second ring.

One edge of the sheet may be longer than the other. The second edge maybe longer than the first edge. At least one of the rings may bepositioned between the first and second edges.

The material of the dispensing means may be oriented at an angle αsubstantially between 15 and 45° to said notional axis. In alternativeembodiments, the angle may be up to about 60° or 70°, or down to about5° or 10°. In embodiments, angle α may be substantially 5, 10, 15, 20,25, 30, 35, 40, 45, 50, 55, 60, 65, or 70°. The angle α is defined asthe angle between the notional axis and an axis extending along thedirection of the shortest distance between a point on the first edge anda point on the second edge.

The screen may additionally comprise one or more supports or mounts,which hold the sheet in a predetermined shape/configuration. The sheetmay be held in shape by such a support at or adjacent each edge of thescreen. The supports may be substantially parallel.

The sheet may be formed of a woven material. The material may bestretchable and resilient. The material may be tensioned, for example bythe supports by which it is held in shape. The sheet may have a minimumextent laterally from a notional axis extending between the two edgesaway from one of the edges, which is larger than the minimum lateralextent from the notional axis at each of the edges. A further supportmay be provided between the edges of the sheet, to hold a ring of thesheet to a larger minimum distance laterally from the notional axis thanat least one of the edges. The supports may be generally circular.

The sheet of material may be substantially conical or frustoconical.

The first ring and the first edge may be coincident, the second ring andthe second edge may also or alternatively be coincident. Alternatively,the first ring and the second edge may be coincident. The first and/orsecond rings may be located between the first and second edges. Thefirst and second rings may be substantially circular, oval, square, orany other polygonal shape. A notional ring of the material between thetwo edges may have a minimum lateral extent from the notional axisbetween the edges more than that at each edge.

In general, the volatile material is applied to the dispensing screen ina liquid carrier at the first edge, and the volatile material in theliquid carrier flows towards the second edge by capillary action,gravity or a combination of both, evaporating as it flows. Inembodiments where gravity is used to propel the flow of material downthe sheet, the convoluted path may reduce the apparent effect of gravityby preventing a fully vertical flow of the material down the sheet. Thegravity flow removes the need for a power source to pump material.Further, application of fresh volatile material to the top of the sheetin embodiments washes any residue from previously applied material downthe sheet to reduce clogging and the consequent reduction inperformance. The sheet is effectively irrigated by newly applied carrierliquid and volatile material to “wash” down already applied material andkeep the sheet clear for carrying more material for evaporation. Theconvoluted path increases the path length for any given size of sheet.The sheet can therefore be made more compact than would otherwise bepossible, and extra structural features to support the sheet can bereduced. These factors may also serve to reduce cost of manufacture ofthe sheet.

Such a screen can produce constant or near-constant evaporation of thevolatile material, and also consistent ratios of the different chemicalsin the volatile material over time. Therefore the odour intensity, andthe particular scent, do not substantially change over the lifetime ofthe dispenser. In the case of an insecticide, insect repellent,anti-viral/bacterial, decongestant inhalant, pheromone or attractantmaterial use, the dispensing is constant, so the dosage of materialsreleased is also substantially constant.

The reservoir may be as shown in U.S. Pat. No. 7,360,671 or U.S. Pat.No. 6,631,891, the entire contents of each of which are incorporatedherein by reference. In this case, a reservoir is provided, in whichvolatile material is contained. A wick extends substantially verticallydown into the reservoir. The sheet may be positioned relative to thereservoir to allow siphonic feeding of the volatile material to the topof the sheet, at the first edge. Alternatively, and preferably, the wickmay be fed by the constant hydrostatic head provided by the pressurecompensated reservoir disclosed in U.S. Pat. No. 7,360,671. Theeffective constant height of the bottom of the reservoir when using thedispenser described in these two documents provides a substantiallyconstant flow rate of volatile material to the top of the sheet.

Capillary and gravity forces combine together to load the dispensingsheet. Gravity becomes more dominant as the capillary force diminishesas the sheet becomes loaded. Gravity acts vertically downwards on eachmolecule of liquid in a column, singularly and collectively. Therefore,a straight path, which was aligned vertically, may make the liquid flowdown the sheet too fast to provide sufficient time for evaporation.

It can be seen that the path taken by a single molecule on the sheetwith a herring bone pattern/sexangular mesh fabric is convoluted. As ittravels from the top to the bottom of the screen along the ‘convolutedpath’, the distance is greater than the actual vertical length of thescreen, ie the shortest length along the surface of the screen from thefirst edge to the second edge. The evaporating capacity may be directlyproportional to the surface area of the, or each, screen. The convolutedpath may comprise a plurality of fluid pathways. The number of fluidpathways may change between the first edge and the second edge of thesheet. The number of fluid pathways may increase from the first edge tothe second edge of the sheet.

The other effect is gravity, acting on each liquid molecule singularlyand the whole column collectively. Most of the path taken by the liquidcolumn is disposed at an angle (inclined plane) to the vertical. Thisslows down the effect of gravity acting on the column of liquid. Theprovision of perforations in the surface of the sheet makes it highlypermeable and therefore very sensitive to any small movement ofsurrounding air. Further, in the case of a woven material such as asexangular mesh fabric, the tension applied to the opposing edges willaffect the speed of travel of the liquid on the sheet. In particular,with higher tension, the spaces are stretched in one direction, and tendto be squashed perpendicular to that direction. Thus, the degree ofconvolution of the woven fibres from the opposing edges is reduced. Evenif the sheet is not squashed by the applied tension in a directionperpendicular thereto, the portions of the woven material that form thesides which are neither horizontal nor vertical will be made closer tovertical, and gravity will therefore pull the volatile material down thesheet more quickly. The material can be highly permeable to air, due tothe high surface area of the strands relative to the surface area of thesheet if it were solid. The strands may be fine polyester monofilaments,which may be woven into the sheet of the screen. The material may beself irrigating.

It can also be seen that the convoluted path influences the fragrancematerial to encircle each and every hole in the surface of the sheetwhen travelling from the top of the screen towards the bottom. Capillaryforces combine with gravity in helping to distribute the fragranceuniformly across the sheet's surface.

In embodiments, the wick feeds the sheet by siphonic action. However,alternatively, where a liquid has a low volatility and a low viscosityis used, siphonic action may not be used. An example is the liquidEXXSOL D 40, ISOPAR-L and ISOPAR-M which is used as a carrier for aningredient to kill mosquitoes. In the present embodiments the activeingredient is in a low concentration between approx 0.5 and 2%.Preferably, the concentration is between approximately 0.89 and 1.78%,as this has been found to be effective. It will, however, be appreciatedthat other concentrations could be employed, and particularly if adifferent carrier is used. Other possible carriers could be used subjectto testing of volatility and performance. These are: EXXSOL D80 andEXXSOL D100.

How far the liquid travels around the fabric circuit depends upon thetemperature. As the temperature increases, there is an increase in thevolatility of the liquid product and therefore the liquid evaporates ata faster rate and will only travel a relatively short distance along thepathway. When the temperature is lower, the volatility of the liquid isreduced and evaporated at a lower rate. Therefore the liquid, onaverage, travels to a point further along the pathway beforeevaporating. The temperature compensation effect can be seen as theresult of a higher volatility of product dispensed from a smallersurface area equates to a lower volatility of product evaporated over alarger surface area.

Aspects and embodiments of the invention are therefore, for the variousreasons given above, particularly suitable for dispensing low volatilityliquid insecticides.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention will now be described, purely by way ofexample, with reference to the accompanying figures, in which:

FIG. 1, discloses a dispensing screen comprising a cylindrical sheet ofmaterial that has been stretched from its cylindrical endslongitudinally;

FIGS. 2 and 3 show the effect of this longitudinal stretching on a sheetof woven material comprising the screen;

FIG. 4 shows a dispensing screen according to a first embodiment of theinvention;

FIG. 5 shows a cross section at one end of the screen shown in FIG. 4;

FIG. 6 shows a longitudinal cross section of the screen of FIG. 4through a notional axis;

FIG. 7 shows a dispenser according to a second embodiment of theinvention incorporating a dispensing screen according to the firstembodiment of the invention;

FIG. 8 shows the effective heights required of cylindrical andfrustoconical screen shapes to achieve the same surface area dimensions;

FIG. 9 shows, schematically, the relative heights of the dispensingscreen and the dispenser of FIG. 7;

FIG. 10 shows a dispenser according to a third embodiment of theinvention;

FIGS. 11 a, b, and c show a modification of the dispensing screen shownin FIG. 7;

FIG. 12 shows a reservoir for use in embodiments of the presentinvention;

FIGS. 13 and 14 show a dispenser according to a further aspect of theinvention; and

FIG. 15 shows a sheet for use in embodiments of the invention.

Turning now to FIGS. 1 and 2, FIG. 1 shows a dispersal screen 10comprising two circular supports 12, 14, at the bottom and the top. Asheet of material 16 is provided, extending between the circularsupports 12, 14. The sheet 16 of the present embodiment is formed from aflexible, stretchable, and resilient woven material, having a highpermeability to air, so it is necessary for it to be tensionedlengthwise between the top and the bottom as indicated by the arrows, inorder that it maintains its shape.

In the present embodiment the material is Litmans 573, which has a lowloading capacity for volatile liquids. The material has a highcapillarity, but low absorbency. To provide good permeability, the sheethas a high void ratio and when it is pulled taut from the top to bottomto secure it to the support, these holes in the fabric structure becomeelongated. However, this produces the effect shown in FIG. 1 where awaist is formed in the wall of the sheet of the dispersal screen.Litmans 573, being a woven or mesh material, made from polyester, isparticularly useful for emanating insecticides, which are typically lowvolatility liquids. Litmans 573 provides high exposure of surface areafor the emanation. Using polyester is advantageous due its resistance tosolvents and the smoothness of its surfaces that aids its capillarity.

FIG. 2 (for clarity on a black background) shows how the hexagonal holesin the woven tensioned material of the sheet 16 in FIG. 1 becomedeformed by becoming elongated when subjected to tension in a singledirection, in this case along the cylindrical axis. This shows thedeformation of the cylindrical sheet. There are several adverse effectsof this: 1) the fibre density per square centimetre is increased; 2) thepermeability to air is reduced; 3) the grain of the pattern isvertically biased; 4) the loading of liquid on the screen is increased;5) the increase in saturation of liquid on the sheet 16 reduces theeffective evaporative surface of the woven fabric of the sheet.

In FIG. 3 (again for clarity on a black background) it can be seen thatthis sheet is evenly tensioned between the cylindrical axial andcircumferential directions. The configuration in FIG. 3 has a lowerfibre density than that shown in FIG. 2 and greater permeability to air.This will have a lower loading of liquid and as a result have a higherevaporative surface area. Further, because the elongation is no longeronly along the cylindrical axis, the angle of each of the weaves extendsto a greater degree across the cylindrical axis, so increasing theminimum path length for volatile material travelling down the cylinder,and slowing the rate of descent of the volatile material when it isapplied to one cylindrical end of the screen, which is orientated withits cylindrical axis substantially vertically, and moves move slowlydown the material.

FIG. 4 shows a means for achieving the configuration of the sheet 16shown in FIG. 3. A part conical support structure for the sheet isprovided and, although the tension is applied between the top and thebottom of the structure (as in the case of the cylinder in FIG. 1), avery different result is provided, due to the angle produced by the twodiameters and the distance between them. The support structure of FIG. 4provides a material structure substantially according to FIG. 3. Thecurved dotted lines 18 indicate how the woven fabric forms around thestructure. The structure is formed of two concentric and parallelcircular supports 20, 22, which are separated from one another. Theupper support 20 is of smaller diameter than the lower support 22.Holding the structure together and maintaining the separation of theupper and lower supports 20, 22, are three rods 24. The rods may bejoined with the supports by any convenient method. With this arrangementtension can be applied to the material as the rods 24 counter thecompressive force between the upper and lower supports 20, 22. The upperand lower supports 20, 22 are formed substantially open, so as toimprove air flow around the screen 10.

In the present embodiment, the supports 20, 22 are each formed of twoconcentric, coplanar, annular rings, joined by three radial braces 26 a,26 b. The upper support 20 comprises a lip or flange 28, which allows awicking element, not shown, to be placed in the recess formed thereby totransport the volatile material from a central hole in the upper support20, in which is placed a porous stud, and to which a reservoir holdingthe volatile material (not shown) is coupled, to the outer circumferenceof the upper support 20, to which the sheet 16 is coupled. The sheet 16is coupled to the support and the wick via known methods. A ring isprovided (not shown), mounted over the wick and sheet and attached tothe upper support, by a friction fit. Alternatively, adhesive ormechanical means may be used to secure the ring, for example.

FIG. 5 shows a stamped out wick 29, in the present embodiment in theform of a paper element that connects between the porous stud in themiddle at the top of the upper support and the top of the sheet. It fitsinside the recess at the top of the support 20 and is retained incontact with the top of the screen by a ring (not shown).

FIG. 6 shows a profile (side view) of the screen, comprising the sheet16 fitted to the frustoconical support structure shown in FIG. 4. Inthis embodiment, the diameter of the lower support 22 is twice thediameter of the upper support 20.

FIG. 7 shows the dispensing screen 10 with the reservoir/cartridge 32installed to form a dispenser 30. The cutaway section shows how thesheet 16 is secured to the upper support 20, via the ring 34. The porouswicking element 29 is also shown. The first (upper) edge 21 of the sheetis mounted on the upper support 20 as discussed above. The second(lower) edge 23 of the sheet 16 is glued to the lower support 22.

The sheet 16 is mounted on the circular supports 20, 22 and thus has asubstantially circular cross section substantially normal to the axis ofthe screen. A first closed notional ring on the surface of the materialof the sheet 16 has a first length around its circumference and a secondclosed notional ring on the surface of the material, substantiallyparallel thereto and separated therefrom, has a second length around itscircumference, the second length being longer than the first length. Thenotional rings in the present embodiment are substantially normal to theaxis of the screen. It can be seen that the area of the cross sectionthrough the first ring is smaller than the area of the cross sectionthrough the second ring. The minimum distance from a notional axisthrough both rings, in the present embodiment the rotational axis ofsymmetry of the screen, of the first ring is smaller than the minimumdistance from the same notional axis of the second ring. In the presentembodiment, the first notional ring is a first edge 21, at or adjacentthe upper support 20. The second notional ring is a second edge 23, ator adjacent the lower support 22.

The configuration means that the sheet of material is angled at an angleα to an in use vertical axis (V) of the dispenser along the materialfrom the first to the second edge. In the present embodiment, the anglechanges with the position along the axis, but remains acute. FIG. 7shows how angle α is defined as the angle between the vertical axis (V)and an axis extending along the direction of the minimum distancebetween a point on the circumference of the first support and a point onthe circumference of the second support. In other embodiments, the angleα may remain constant along the length of the sheet 16 from the firstedge 21 to the second edge 23. In either case, the angle α may besubstantially between 15 and 45°, e.g. typically 30°. It has been foundthat an angle within this range is sufficient to provide the advantagespreviously described, without extending too far in a directionperpendicular to the vertical axis V, which would be undesirable whenthe products are placed on shelves for retail. It will, however, beappreciated that other angles may be employed, e.g. up to about 60° or70°, or down to about 5° or 10°. That is to say, the angle α may besubstantially 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70°.

The mesh screen 10, by being formed into a cone or cone-like shape,provides a progressive increase in structural routes to the path of theliquid product. This effect, combined with the screen's high evaporativeability maintains an even loading of liquid over the fibrous structuressurfaces of the screen 10 from the top to the bottom. If the screen 10was formed into a cylinder, the loading at the bottom would be higherthan the upper part of the screen.

FIGS. 8 A and B show how a cylindrical sheet has to be much longer thana frustoconical sheet in order to be equivalent in surface areadimensions. A ramification of this (apart from other adverse effectsthat were mentioned earlier) is the saturation of the material thatwould be caused by the head height of a column of liquid located in thesheet's woven fabric structure. It can also be seen that thefrustoconical configuration is much shorter, and therefore verticallycompact, than the cylindrical configuration.

FIG. 9 illustrates the height difference between the reservoir 32 andthe sheet of the dispenser 30. Firstly it can be seen from the drawingthat the supply system is hydrostatically negatively biased. This isillustrated by the large differences in height between ‘h’ and ‘H’. Thisdifference is much larger than a cylindrical emanating system with thesame surface area, as shown in FIGS. 8 A and B. In embodiments of thepresent invention, flow is thus controlled by the negative hydrostaticforce of the fluid circuit that is created by the different heights hand H. Once the fluid circuit is primed by capillary action, thenegative hydrostatic force attenuates the flow against which thecapillary circuit forces pull.

The resilience of the material in the sheet 16 causes the material tocurve radially inwardly. This curvature of the sheet provides a changingangle of the sheet to the vertical, which can be beneficial. Thischanges the effect of gravity along the axial extent of the screen, ievertically, in use. As the liquid product travels down the sheet 16, itsincrease in head height is less relative to its increase in surfacearea, unlike a cylindrical support, where the head height increases atthe same rate. The sheet 16 discriminates between the carrier and theactive ingredient by the higher volatility carrier mostly evaporatingfrom the radially smaller upper part of the sheet 16, and the lowervolatility active material mostly evaporates from the radially largerlower part of the screen.

FIG. 10 shows an alternative embodiment, where the support structurecomprises three supports 120, 122, 140, rather than simply an upper anda lower support. Once again the supports 120, 122, 140 are axiallyseparated, parallel and concentric. However, the upper and lowersupports 120, 122 now have the same radius, while a central support 140is placed axially between them. The upper support 120 is formed in asimilar manner as described above, including the wicking element 136,ring (not shown) and lip or flange 128. However, as shown in FIG. 11A,the inner concentric ring and radial braces are not provided in thisembodiment. In the present embodiment, the lower support 120 comprises aring (not shown), similar to the ring associated with the upper support,although without the need for a porous wicking element. Alternatively,the sheet 116 may be glued or otherwise attached to the lower support.The central support 140 is maintained in position, in the presentembodiment substantially mid way between the upper and lower supports,by rods 124, in the same way as in the earlier embodiment. Only one ofthe rods 124 is shown in the Figure for clarity. Although not shown, thecentral support also has the same structure as the upper and lowersupports. The central support 140 comprises two concentric, coplanarannular rings, the rods 124 being attached to the inner ring, andmaintaining the separation between the upper and lower supports. Thisstructure allows air movement within the axial extent of the sheet.

A base 150 is provided, on which the lower support 122 is held to holdthe dispensing screen in place. In the present embodiment, the lowersupport also comprises a lip or flange, into which the base is placed.The rods 124 connecting the central support 140 and the lower support122 extend through the lower support 122 and engage with correspondingholes in the base 150.

FIGS. 11 A, B and C show components of the dispenser of the secondembodiment. The central support 140 comprises a pair of coplanar,concentric annular rings 142, 144, connected and held in relativeposition by three braces 145. Holes 146, 148 are provided for receivingthe separating rods 124. The holes alternately receive rods between thecentral support 140 and the upper support 120 and the lower support 122.

FIG. 12 shows a reservoir according to embodiments of the presentinvention. As described above, the reservoir is as described in U.S.Pat. No. 7,360,671. The reservoir 32 comprises a body 36, in which thevolatile material is contained, a base 37, and a dispensing piece 38 atthe top, which houses a wick and a porous stud to conduct the volatilematerial out of the reservoir 32 and which engages with the porousmaterial 34, which allows communication of the volatile material to thesheet 16. The dispensing piece comprises a circular part, which engageswith the inner circumference of the inner ring of the upper support, inorder to mount the upper support, and thus the screen, on the reservoir,which also serves as the base of the dispenser.

FIG. 13 shows an alternative dispenser according to embodiment of theinvention. The screen 210 is similar to the screen described above, andthe reservoir 232 is as described above. However, in this embodiment,the lower edge of the sheet 216 is placed in fluid communication with asink 260, ie material that absorbs any unevaporated material thatreaches the second edge of the sheet 216. Upper and lower supports (notshown) are also provided in the same way as described above. Such anabsorbent sink is particularly useful when the volatile materialcomprises one or more fragrances, where residues may remain, rather thanall of the material supplied by the reservoir evaporating from thesheet, as is the case with some insecticides for example. Oneinsecticide that could be used with embodiments of the invention isSumiOne. This may be used as the active ingredient, this being volatileat room temperature, with e.g. ISOPAR M as a carrier.

FIG. 14 shows a view from underneath the dispenser of FIG. 13. Extendingbetween the sheet 216 and the sink 260 is a sheet of paper 270. The sink260 is wrapped around and secured to the reservoir 232. The base of thereservoir 232 is not covered with the sink 260, so that a user can seewhen the reservoir is empty and replace then reservoir 232 and sink 260together as a single unit. The sheet 216 is mounted on the lower supportas described above. The paper 270 is mounted on the lower support andhas the same shape, and provides a fluid communication path from thesecond edge of the sheet 216 to the sink 260. Where the paper 270connects to the sink 260 a flange is formed on the paper 270 to ensurethe communication for fluid from the paper 270 to the sink 260. Thepositioning of the sink 260 is higher than the constant level in thereservoir 232 so gravity has little effect. Further, the sink 260functions by capillary action upwards so that it deposits the residuesat the top first. It has a uniform cross sectional area. Also, althoughits primary purpose is to filter and collect the residues, it is also agood emanator for the components of the dispensed material with lowervolatility, so that more of the product can be dispensed and less iswasted. A base (not shown) is provided on which the reservoir sits, toprovide stability to the dispenser.

FIG. 15 shows a manner of forming the screen according to all of theabove embodiments. A flat sheet of material is cut into a section of anannular disc of fabric. For clarity, the size of the weave in the fabricis exaggerated many times in the figure. The straight ends of thesection A, B are then joined to form a generally frustoconical shape,which may be curved from top to bottom, with the two arcs forming thefirst and second edges of the sheet 16. As the liquid travels down thesheet 16, the number of liquid pathways increases, progressivelyreducing the loading of liquid on the screen. No stretching force may beapplied to the sheet, which may therefore have a frustoconical shape.Alternatively, the first and/or second edges may be stretched, so thatthe shape is as shown in FIG. 9 or 10 for example.

As a further alternative, a rectangular piece of material, or a sheetwhich is formed in arc, but not circular arcs, may be used as the baseto create the sheet by wrapping the material around to form the closedloop. Thus, the degree of increase of the liquid pathways from one edgeof the sheet to the other can be controlled.

The present invention has been described herein purely by way ofexample, and various additions, omissions and changes would be readilyapparent to one skilled in the art, and therefore also fall within thescope and spirit of the invention. The terms comprise, comprising,comprises are, unless the context clearly demands otherwise, intended tobe interpreted in the inclusive sense, that is, including, but notnecessarily limited to.

1. A dispenser for dispensing volatile material by evaporation, thedispenser comprising: a reservoir, for containing volatile material tobe dispensed; a dispensing screen for dispensing volatile material byevaporation, the dispensing screen comprising a sheet of material havingcontinuous first and second edges and forming a continuous loop ofmaterial extending between the first and second edges; and communicatingmeans, for carrying volatile material from the reservoir to an in useupper edge of the dispensing screen, wherein the material of thedispensing means is acutely angled to an in use vertical axis of thedispenser.
 2. A dispenser according to claim 1, wherein the dispensingscreen is mounted around the reservoir.
 3. A dispenser according toclaim 1, wherein the dispensing screen is mounted concentric to the inuse vertical axis of the reservoir.
 4. A dispenser according to claim 1,wherein the communicating means comprises a wicking element, extendingfrom inside the reservoir to the first edge of the dispersing screen. 5.A dispenser according to claim 1, wherein the communicating meanscomprises more than one wicking elements arranged between the reservoirand the screen, the wicking elements in communication with one anotherto deliver volatile material from the reservoir to the screen.
 6. Adispenser according to claim 1, wherein the height of the dispensingscreen is the same or less than the height of the reservoir.
 7. Adispensing screen for dispensing, by evaporation, volatile materialsapplied thereto, the screen comprising: a sheet of material; anddiverting means formed in or on the sheet, wherein the diverting meansform a minimum path length of the sheet for volatile material flowingalong it between at least a portion of a first edge and an opposingsecond edge of the sheet, which minimum path length is longer than theshortest distance between the first and second edges along the surfaceof the sheet, wherein the first and second edges of the sheet are eachjoined so that each is continuous, and the sheet is formed into acontinuous loop of material between them, and wherein a first closednotional ring on the surface of the material has a first length aroundits circumference and a second closed notional ring on the surface ofthe material, substantially parallel thereto and separated therefrom,has a second length around its circumference, the second length beinglonger than the first length.
 8. A dispensing screen according to claim7, wherein one edge is longer than the other.
 9. A dispensing screenaccording to claim 8, wherein the second edge is longer than the firstedge.
 10. A dispensing screen according to claim 7, wherein at least oneof the loops is situated between the first and second edges.
 11. Adispensing screen according to claim 7, wherein the sheet is held inshape by a support at or adjacent each edge of the screen.
 12. Adispensing screen according to claim 11, wherein the supports aresubstantially parallel.
 13. A dispensing screen according to claim 7,wherein the sheet is formed of a woven material.
 14. A dispensing screenaccording to claim 7, wherein the material is stretchable and resilient.15. A dispensing screen according to claim 7, wherein the sheet ofmaterial is substantially conical or frustoconical.
 16. A dispensingscreen according to claim 7, wherein the sheet of material is tensioned.17. A dispensing screen according to claim 7, wherein the divertingmeans comprises a plurality of fluid pathways, and the number of fluidpathways increases from the first edge to the second edge of the sheet.18. (canceled)
 19. A dispenser according to claim 1, wherein a furthersupport is provided between the two edges, and parallel thereto, to holda ring of the sheet to a larger minimum distance laterally from thenotional axis than at least one of the edges. 20.-21. (canceled)